The Conservatives have finally broken through the glass ceiling of 30 per cent support in the polls. Paradoxically, this is a dangerous moment for them.

The growth of the Liberals into the low 30s, as the NDP declined into the mid-to-high 20s, suggests an emerging two-party race in which the Grits could become the clear choice of voters who want change.

Tuesday’s daily Nanos tracking poll is a case in point. It shows the Conservatives at 33 per cent, the Liberals at 31 per cent, and the NDP at 27 per cent. An Abacus poll on Monday had the Conservatives at 32 per cent, the Liberals at 29 per cent and the NDP at 27 per cent.

Within the margin of error, it’s still a very competitive three-way race. The Conservatives, no less than the NDP, are counting on it. The Tories should be very concerned about strategic voters moving from the NDP to the Liberals on the ballot question of change. As for the NDP, they need to shore up their poll numbers and regain momentum in Ontario and Quebec.

This is a big moment, right here, right now. Perhaps Tom Mulcair will be more comfortable, and less equivocal, as the underdog rather than the front-runner.

In Ontario, the NDP has been outflanked by the Liberals on the left. In Quebec, the NDP has been squeezed by the identity politics of the niqab debate.

In Ontario, the Liberals have regained progressive voters through Justin Trudeau’s promise to run a stimulative deficit of $10 billion in each of the next two years and a third deficit the following year before balancing the books in 2019.

Mulcair, meanwhile, is stuck with his pledge to keep the books balanced, as they are now. One of his senior advisers explained the logic: “We can’t run a deficit. We’re the NDP.” Voters in Ontario and British Columbia remember the fiscal chaos under NDP provincial governments. The new NDP government of Rachel Notley in Alberta inherited a $6 billion deficit from the Conservatives, a situation that won’t improve with oil at $45 a barrel. The Notley effect, which drove the NDP national numbers into the 30s after her election in May, has clearly faded during the federal campaign.

Mulcair’s challenge now is to come from behind. And it’s all on his shoulders.

In Ontario, it’s no coincidence that the Liberals have positioned themselves to the left of the NDP, as Kathleen Wynne did against Andrea Horwath in the 2014 provincial election. The same people who ran Wynne’s campaign are running Justin Trudeau’s, with the same progressive playbook.

In Quebec, the niqab issue has taken a toll on the NDP’s lead, particularly off the island of Montreal. It isn’t just the Conservative position — that a woman should show her face at a citizenship ceremony — that’s been driving down the NDP’s poll numbers. This hot-button issue has been driven by the Bloc Québécois’ animated attack ad in which spilled pipeline oil morphs into a woman wearing a niqab. As despicable as the 20-second spot is, it’s effective: the Bloc says it’s had over a million views on the party’s website.

And in the CBC’s Vote Compass audience panel in Quebec, Gilles Duceppe was judged the winner of last Thursday’s French debate by 29 per cent of participants; 20 per cent thought Stephen Harper won, and 18 per cent chose Mulcair and only 8 per cent picked Trudeau.

Trudeau was savaged by the French-language media both for his reliance on talking points and his French grammar and sentence construction. “Justin Trudeau and his cassettes” went the headline on Lysiane Gagnon’s weekend column in La Presse. “His language level, in French,” wrote the doyenne of Quebec pundits, “is that of an anglophone CEGEP student who spent a few years in an immersion class.” Ouch.

Trudeau fared much better, in performance and reviews, and in both languages, in Monday night’s bilingual Munk Debate on foreign policy in Toronto. It was easily the best, and the best-run, of the four leaders’ debates so far, with a lively and engaged audience at Toronto’s Roy Thomson Hall that served as a giant focus group on the leaders’ answers. Having just the leaders of the Big Three parties on stage made it easier to manage the traffic, and moderator Rudyard Griffiths did an outstanding job of keeping the leaders on topic.

There were no losers on the night, but Trudeau may have gained the most in terms of proving that he belonged on that stage, and had his mind wrapped around his briefing notes. Harper looked calm, cool and collected, while Mulcair was scrappy, even chippy at times. In hockey terms, he had his elbows up in the corners.

Now his challenge is to come from behind. And it’s all on his shoulders.

In the 1988 election, Brian Mulroney took a major hit from John Turner in the English debate when the Liberal leader said, “I believe you have sold us out” on free trade.

Conservative poll numbers tanked overnight and in the days that followed the Liberals opened up a double-digit lead. The following week, as Mulroney’s campaign plane was about to fly from Ottawa to the West Coast, I went to the forward cabin to give him his speaking notes for the first event in Vancouver.

“How do you feel?” I asked.

“He’s got the momentum,” Mulroney replied. “Now we’re going to find out what we’re made of.”

That western swing was a defining leadership moment, when Mulroney carried the campaign on his back, reversed the trend and won a majority government.

Tom Mulcair is at such a moment now. The NDP, and the country, are going to find out what he’s made of.

L. Ian MacDonald is editor of Policy, the bi-monthly magazine of Canadian politics and public policy. He is the author of five books. He served as chief speechwriter to Prime Minister Brian Mulroney from 1985-88, and later as head of the public affairs division of the Canadian Embassy in Washington from 1992-94.The views, opinions and positions expressed by all iPolitics columnists and contributors are the author’s alone. They do not inherently or expressly reflect the views, opinions and/or positions of iPolitics.

The views, opinions and positions expressed by all iPolitics columnists and contributors are the author’s alone. They do not inherently or expressly reflect the views, opinions and/or positions of iPolitics.